Plotinus’s philosophy begins with the question about the origin of all things. In a throwback to the Aristotelian theory of the existence of a First Cause of all things Plotinus holds that there is a source from which everything that exists originates. Then he speculates about the nature of this first principle. He calls the primal source of everything the One (Monos). From the One proceeds, through a process of emanation, Intelligence (or Mind) and from Intelligence proceeds the Soul. These three together make up the world of the Intelligibles. At the lower level of reality is the matter, the world of the sensibles; it also proceeds ultimately from the One.
Thus in Plotinus we have a picture of reality that is unified in so far as everything that exists proceeds from one single principle, is sustained by it in being finally returns to it. The question of the One and Many that puzzled the Greek mind from the inception of philosophy is taken up once again and answered in a novel way.
The One (Monos): The origin of everything, the first principle is what Plotinus calls ‘the One’. But what is the nature of this principle? How to conceive of it with more definiteness? He speculates that it must be beyond being, because the original must be outside the derived; and whatever is derived is being. Thus the primal source of everything is not a being but lies beyond being. It is also beyond thought. He rejects Aristotelian view that the First Cause of all is a self-thinking thought. For him to attribute thought to the source of all things is to abrogate its primacy, because with Parmenides he equates thought and being: “to think and to be are the same thing”. Thus if the source of everything is beyond being it should also be beyond thought.
The One does not think, neither of itself nor of other things. He derives the absolute absence of thought in the primal source also from the fact that it is a perfect unity, a One having no plurality or multiplicity whatever. The lack of plurality and multiplicity in the primal source is asserted on the ground that if it has to be the ultimate source of everything there should not be anything else besides itself. If that is granted then it can be also argued that there is no thought in him, because to think is to think of something and therefore implies plurality. There is also no volition in the One, for willing too implies the distinction between the one who wills and that which is willed. It has no qualities, for qualities imply the distinction between subject and predicate. Nothing can be predicated of it; even to say that “it is One” or that “the One is”, is false, because it is beyond all being and essence. No name can be applied to it; it eludes all definition and knowledge. It is neither in movement nor at rest. Since it has no parts, it is without structure and without form. The One is not only the source of everything, but is also the ultimate goal towards which everything else strives. Therefore, Plotinus calls it also the Good.